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AGN-host connection at 0.5 < z < 2.5: A rapid evolution of AGN fraction in red galaxies during the last 10 Gyr

Wang, Tao; Elbaz, D.; Alexander, D.M.; Xue, Y.Q.; Gabor, J.M.; Juneau, S.; Schreiber, C.; Zheng, X.-Z.; Wuyts, S.; Shi, Y.; Daddi, E.; Shu, X.-W.; Fang, G.-W.; Huang, J.-S.; Luo, B.; Gu, Q.-S.

AGN-host connection at 0.5 < z < 2.5: A rapid evolution of AGN fraction in red galaxies during the last 10 Gyr Thumbnail


Tao Wang

D. Elbaz

Y.Q. Xue

J.M. Gabor

S. Juneau

C. Schreiber

X.-Z. Zheng

S. Wuyts

Y. Shi

E. Daddi

X.-W. Shu

G.-W. Fang

J.-S. Huang

B. Luo

Q.-S. Gu


We explore the dependence of the incidence of moderate-luminosity (L0.5−8 keV = 1041.9−43.7 erg s-1) active galactic nuclei (AGNs) and the distribution of their accretion rates on host color at 0.5 1010 M⊙. We use extinction-corrected rest-frame U−V colors to divide both AGN hosts and non-AGN galaxies into red sequence (red), green valley (green), and blue cloud (blue) populations. We find that the fraction of galaxies hosting an AGN at fixed X-ray luminosity increases with stellar mass and redshift for all the three galaxy populations, independent of their colors. However, both the AGN fraction at fixed stellar mass and its evolution with redshift are clearly dependent on host colors. Most notably, red galaxies have the lowest AGN fraction (~5%) at z ~ 1 yet with most rapid evolution with redshift, increasing by a factor of ~5 (24%) at z ~ 2. Green galaxies exhibit the highest AGN fraction across all redshifts, which is most pronounced at z ~ 2 with more than half of them hosting an AGN at M∗ > 1010.6 M⊙. Together with the high AGN fraction in red galaxies at z ~ 2, this indicates that (X-ray) AGNs could be important in both transforming (quenching) star-forming galaxies into quiescent ones and subsequently maintaining their quiescence at high redshift. Furthermore, consistent with previous studies at lower redshifts, we show that the probability of hosting an AGN for the total galaxy population can be characterized by a universal Eddington ratio (as approximated by LX/M∗) distribution (p(λEdd) ~ λEdd-0.4), which is independent on host mass. Yet consistent with their different AGN fractions, galaxies with different colors appear to also have different p(λEdd) with red galaxies exhibiting more rapid redshift evolution compared with that for green and blue galaxies. Evidence for a steeper power-law distribution of p(λEdd) in red galaxies (p(λEdd) ~ λEdd-0.6) is also presented, though larger samples are needed to confirm. These results suggest that the AGN accretion or the growth of supermassive black holes is related to their host properties, and may also influence their hosts in a different mode dependent on the host color.


Wang, T., Elbaz, D., Alexander, D., Xue, Y., Gabor, J., Juneau, S., …Gu, Q. (2017). AGN-host connection at 0.5 < z < 2.5: A rapid evolution of AGN fraction in red galaxies during the last 10 Gyr. Astronomy & Astrophysics, 601, Article A63.

Journal Article Type Article
Acceptance Date Jan 11, 2017
Online Publication Date May 3, 2017
Publication Date May 3, 2017
Deposit Date Jun 21, 2017
Publicly Available Date Jun 30, 2017
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 601
Article Number A63
Public URL


Published Journal Article (5.2 Mb)

Copyright Statement
Reproduced with permission from Astronomy & Astrophysics, © ESO 2017

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